2-Cyano-3,3-diarylacrylates, with structural Formula I, is widely used in creams and lotions as a Sun protection factor (SPF) booster. The extended conjugation of the acrylate portion of the molecule absorbs UVB and short-wave UVA (ultraviolet) rays with wavelengths from 280 to 320 nm.

2-Cyano-3,3-diarylacrylates are generally prepared by the Knoevenagel condensation of either 1) Cyanoacetic ester with Arylketone or 2) Alkyl cyanoacetate with Arylketone followed by transesterification with alcohol.
Compounds of Formula I were first disclosed in U.S. Pat. No. 3,215,725 wherein the process for preparation is also disclosed. This process involves reaction of Arylketone with ethylene glycol di-(□-cyanoacetate) in the presence of ammonium acetate, glacial acetic acid in benzene. However, the drawback of this process is that the product formed is discolored and therefore the purification is extremely laborious.
U.S. Pat. No. 5,047,571 describes a process for preparation of 2-Cyano-3,3-diarylacrylates by transesterification with alcohol at 130° C. in presence of basic catalyst with continuous removal of resulting alcohol. The resulting product was purified by film evaporation process.
Most of the patents describe the use of organic solvents for the removal of water of reaction azeotropically. U.S. Pat. No. 2,623,060 discloses use of aromatic solvents for the removal of water of reaction azeotropically. U.S. Pat. Nos. 3,337,357, 3,544,466 and 4,207,523 disclose a general method for making substituted phenylcinnamates wherein the reactants are combined with an aromatic solvent and catalyst, heated to reflux, wherein water is removed and the product is recovered from the solvent. These patents generally give a yield of 60 percent to 70 percent product.
EP0430023 discloses the preparation of 2-Cyano-3,3-diarylacrylates by reaction of Arylketone with cyanoacetic acid ester in the presence of ammonium acetate and glacial acetic acid using heptane for the removal of water of reaction azeotropically. The process involves long reaction time and use of metering pump to add the catalyst periodically through the course of the reaction.
U.S. Pat. No. 5,451,694 discloses the process of making 2-Cyanocinnamic esters in organic solvent such as Propanoic acid. However, comparative example I conducted as per the process given in this patent, indicates significant generation of Biphenyl cyanoacrylamide (BPCA). Further, the process is not economical due to cost and availability of C3-C6 monocarboxylic acids.
Patent application 2831/MUM/2010 discloses the preparation of substituted Diphenylcyanoacrylate compounds using cyclohexane, hexane or toluene as solvent.
All the processes of the prior art require long reaction times for obtaining high yields, thereby leading to more formation of unwanted impurities like Diaryl cyanoacrylamide. Besides this, the use of aromatic solvent puts restriction on commercial proposition of these routes due to carcinogenicity of aromatic solvents, in addition to increase in the cost.
Hence, there is a need to develop an, efficient and industrially viable process for the preparation of 2-Cyano-3,3-diarylacrylates.
Accordingly it is an object of the present invention to provide a cost-effective process for the preparation of 2-Cyano-3,3-diarylacrylates from Arylketone and Cyanoacetic ester with high yields and good purity.
In achieving the above objective, the inventors of present invention have developed a process to obtain 2-Cyano-3,3-diarylacrylates using acetic acid and ammonium compound with very good control over the formation of Diaryl cyanoacrylamide (<0.2%) in reaction mass. Further, the process of the present invention does not involve any organic solvent for removal of water of reaction. The process is cost effective, operationally simple, exploits cheap and commercially available raw material, acetic acid, with very good conversion under reduced pressure with a control over impurities. Further the recovered acetic acid can be reused as such or after removal of water.